Expansion joints are required between, for example, two duct sections traversed by hot gases, between conduits or the like forming part of chemical or metallurgical process equipment or systems in which expansion and contraction phenomena mandate some mobility in the joint, and wherever a gas-tight joint is required and where corrosion or aggressive attack on the joint is a problem.
In all of these cases, elastomeric materials, which can normally span a fluid-tight joint between two duct members cannot be used because the high temperatures and aggressive nature of the gases would cause deterioration of the seals. Conventional labyrinth seals also cannot be used where truly gas tight joints are required and release of gas to the environment is undesirable or a potential problem.